Why is doAttachTransmissionCurve=False by default?
We don't attach TransmissionCurves for most cameras during ISR (isr.doAttachTransmissionCurve also defaults to False), because nobody has compiled that data for anything other than HSC.
An alternative would have been to make both of those steps leave the TransmissionCurve set to None when they don't have the necessary inputs. But I wanted to guard against the case where someone is trying to build a coadd that includes TransmissionCurve propagation and doesn't realize until they get to the end that something went wrong in ISR; I don't feel like even warning helps much, and in any case I wouldn't want to make processing other cameras generate a lot of warnings.
Will do one more Jenkins run with both
DM-12370 and this before merging.